I went touring with some really awesome guys yesterday, and their gadgets were rad. It made me want to know more about what little items really support or increase your enjoyment of slack/side/back country - any suggestions?
In particular, my buddy's compass + declinometer was really neat, as was his small magnifying glass for analyzing snow crystals in a variety of packs. We were on a avalanche safety-specific tour, but despite that, it's amazing how much a tiny piece of kit can improve your hike.
What are your favourite gadgets?